This invention relates in general to the separation of fluid mixtures into their constituents; more particularly to processes and means for the enrichment and/or depletion of solute in a near critical fluid.
The use of near critical and super-critical fluids as solvents to process materials is known from e.g: U.S. Pat. No. 3,969,196 issued July 13, 1976 to Zosel. Existing processes, described in this patent, for example, use a super-critical fluid as a solvent in which a solute is dissolved at one set of conditions of temperature and pressure, and when desired precipitated out by reducing the pressure or increasing the temperature. The current state of technology in this art of Super-critical Fluid Extraction is presented in a book of that name by McHugh and Krukonis, Butterworth Publishers, 1986.
The properties of super-critical fluids can give rise to undesirable results, as when dissolved silica is precipitated out of solution in high pressure steam expanding to drive a turbine. McHugh and Krukonis describe this situation at pages 21 and 22. During production of high-pressure steam silica that is present in water is dissolved when the super-critical steam is made. The silica is transported as dissolved species to the turbines. During the pressure decrease as the steam travels (expands) through the turbine, the silica precipitates out and deposits on the turbine blades, resulting eventually in a shutdown for cleaning.
The present invention, among other things, teaches a new system for driving a turbine with high pressure steam, in which dissolved species are removed from the single-phase of the steam before it reaches the turbine.